High speed water craft

ABSTRACT

A power-driven high speed planing water craft has a screw propeller disposed in a longitudinally extending tunnel opening downwardly along the underside of the hull, the tunnel having a vent opening adapted to admit air, in advance of the propeller, above the water level when the craft is in operation, and preferably having also an abrupt step formation towards the front end. The hull can be moulded as a lightweight unitary structure in glass fiber reinforced plastics and may completely shield the propeller in the tunnel. The craft also preferably has a rudder system comprising a pair of interconnected angularly moveable parallel rudder plates which form a rear extension of the tunnel.

United States Patent [72] Inventor Alan Reider 961,750 6/1910 Branth 114/67 Micltleover, England 1,157,423 /1915 Ryan et a1. 1 14/665 [21] Appl. No. 826,813 2,139,831 12/1938 Langstaff 114/67 [22] Filed May 22,1969 2,772,649 12/1956 Gensheimer et al.. 115/05 [45] Patented Sept. 14,197] 3,371,642 3/1968 Joy 114/665 [73] Assignee Dynamic Developments Limited 3,437,069 4/1969 Bennett.. 1 /34 Leeds, England 3,469,549 9/1969 Rae 1 14/665 Pnomy Primary Examiner-Andrew H. Farrell [3] 1 5132/68 Attorney-Richards & Geler ABSTRACT: A power-driven high speed planing water craft [54] um SPEED WATER cm has a screw propeller disposed in a longitudinally extending 15 claims, 5 Drawing Figs tunnel opening downwardly along the underside of the hull,

the tunnel having a vent opening adapted to admit air, in ad- [52] US. Cl ll4/66.5 Vance of the propeller above the water level when the ft i 1 1 Cl in operation, and preferably having also an abrupt step forma- [50] new 114/665 tion towards the front end. The hull can be moulded as a 63; ls/61,70 lightweight unitary structure in glass fiber reinforced plastics and may completely shield the propeller in the tunnel. The [56] References cled craft also preferably has a rudder system comprising a pair of UNITED STATES PATENTS interconnected angularly moveable parallel rudder plates 128,407 6/1872 MacPherson 1 14/62 which form a rear extension of the tunnel.

49 48 N 11 l7 l6 19 20 50 13 M l 44 4o 21 42 lo I 1 I I 1 L 1 l 12c 14 12b 12 23 I8 35 12a 37 PATENTEDSEPI 41971 SHEET 1 OF 2 INVENTOR: A R e 1.' cl 2 r ATT ILNNS NVENTOR. A M/tier W xiv? SHEET 2 BF 2 ATENTEI] SEP 1 4 l97| 'l r k llll HIGH SPEED WATER CRAFT This invention relates to power-driven water craft designed for high speed planing operation and equipped with screw propeller propulsion means.

From one aspect, the invention consists in a power-driven high speed planing water craft having a screw propeller disposed in a longitudinally extending channel opening downwardly along the underside of the hull, said channel being adapted to permit air to be admitted therein, during operation of the craft, in advance of the propeller and above the water level.

The channel may be in the form of a tunnel of any convenient and suitable cross section such as for example, square, rectangular, semicircular, or inverted U-shape enabling the propeller to be accommodated in full shielded relationship, within the contour of the hull. Preferably the forward end of the main part of the channel or tunnel containing the propeller is also closed or partially closed by a front crosswall which is substantially vertical when the craft is level so as to provide an abrupt well-defined stepped entrance.

For admitting the air, the channel or tunnel may be designed to extend sufficiently forwardly along the hull so that its front end comes clear above the water line when the craft is in an inclined position during planing operation. The main propeller-containing part of the channel or tunnel, however, is preferably substantially shorter than the length of the hull and is disposed towards the rear end of the latter, and a vent opening in addition, or as an alternative, to that provided by a front portion designed to rise clear of the water, may be provided above the water line in the top of the channel or tunnel in front of the propeller. By this means, air is drawn in and tends to relieve the partial vacuum or drop in pressure created therein when the craft is in motion.

The propeller may be carried by a propeller shaft which is supported at the rear end by a bracket carrying a bearing, such as a water lubricated bearing or nylon or other plastics material for example. Power to the front end of the propeller shaft may be transmitted through a front bulkhead partition wall of the channel or tunnel from an engine power unit, either directly or through suitable gearing.

The channel or tunnel may be integrally formed with the hull of the craft and can readily be molded into the hull in the case of a glass fiber reinforced plastic (G.R.P.) construction for example. In another form, however, the channel or tunnel may be part of a separate unit which includes the engine power unit and which is adapted to be attached to the underside of a suitable hull, as by bolts or welding for example.

In a preferred arrangement the rudder system comprises a pair of spaced-apart pivoted or hinged vertical rudder plates at opposite sides of a flared rear end portion of the tunnel which are linked together so as to remain parallel and move in unison, these rudder plates effectively fonning a continuation of the tunnel. Such rudder arrangements provide a high efficiency and enhance maneuverability, especially at slot speeds.

By way of example, one form of lightweight power-driven high speed planing water craft in accordance with the invention is illustrated in the accompanying drawings, wherein:

FIG. I is a side elevational view;

FIG. 2 is a longitudinal sectional view;

FIG. 3 is a plan view;

FIG. 4 is a section on line IV-IV of FIG. 2; and

FIG. 5 is a detail sectional view, on a larger scale, of a flexible coupling unit which connects the propeller shaft to the power unit output.

Referring to the drawings, the craft illustrated therein has a lightweight hull structure which is composed of glass fiber reinforced plastics material and which is provided with an integral deck superstructure l1 and, on the underside, a tunnel formation 12 of inverted U-shape cross section extending forwardly from the stem. The deck superstructure 11 in turn carries a seat fitting l3 and a fuel tank fitting towards the rear.

At the stern, the end of the tunnel 12 is open and the walls flare outwardly, but the rear end portion 12a leading to the stem is of substantiallyuniform depth and cross section. Following forwards, there is then a short intermediate portion 12b of the tunnel which has an increased depth and which terminates at a nearly vertical front wall formed by a bulkhead partition 14 of the hull structure slightly to the rear of the midpoint of the craft. The forward portion of the tunnel, in advance of this bulkhead partition 14 is then of greatly reduced depth, being sufficiently shallow to ensure it lies completely below the water level when the craft is stationary in the water or is moving at low speed, and this portion 12c finally terminates at the front by merging into the curved contour of the undersurface of the hull at a position approximately two-thirds of the length along the craft from the stem.

The power unit of the craft is provided by a rotary-pistontype internal combustion engine 16 which is located in a cockpit compartment 17 forwardly of the bulkhead partition 14 and which is adapted to drive a propeller 18 positioned within the rear end portion 12a of the tunnel.

Conveniently, the engine power unit 16 is fitted with a cast aluminum mounting plate 19 and is bolted in located position to the bulkhead partition 14 through an intermediate mounting plate 20 and a retaining plate 21 at the rear.

The propeller 18 is driven through a propeller shaft 23 which is connected at the forward end through a flexible coupling unit 24, which projects through the plates 19, 20 and 21, to the output shaft of the engine power unit 16, suitable seals such as lip seals being fitted as necessary to prevent entry of water into the cockpit compartment 17.

As shown in more detail in FIG. 5, the flexible coupling unit 24 comprises an outer housing 27 in the form of a flanged sleeve which is adapted to be fixed, as by bolts, and its forward end to a flywheel (not shown) on the engine output drive shaft. Within the housing 27 is contained a flexible coupling member 29 comprising a pair of concentric cylindrical sleeves 30, 31 with rubber or other elastometric material 34 bonded between them, the outer sleeve 30 having a flange 32 at the rear end which is bolted to the housing by three retaining bolts 33 so as to rotate concentrically therewith. The inner sleeve 31 provides a socket connection to the front end of the propeller shaft 23 which is a heavy press fit therein.

At the rear end, the propeller shaft 23 is rotatably supported in a sleeve bearing 35 conveniently formed integrally in a moulded nylon bearing bracket 36 which comprises a central web 37 depending from a baseplate portion 38 fitted to the top of the tunnel immediately adjacent the stern. As shown, the propeller 18 is fitted to the propeller shaft 23, being shrunk in place thereon, immediately in front of the bearing bracket 36, and it is fully accommodated within the interior of the tunnel portion 12a.

The bearing bracket 36 also forms a mounting or anchorage for a pair of control cables 40, 40, for operating the rudder assembly. The later comprises a pair of spaced-apart parallel rudder plates 42, 42, each composed of polypropylene or like moulded plastics material and fixed to the sidewalls of the tunnel section 12a along their front edge portions in advance of a hinge formation 43 which permits the main body of each rudder plate to be moved angularly in a horizontal direction. So that an integral moulding can be used, the hinge formations 43 may comprise vertical grooves or neck portions of reduced thickness towards the front edge of the plates, sufficient flexibility and resiliency being inherent in the polypropylene plastics material of which they are composed then to allow the required angular movement.

The rudder plates 42, 42, in effect provide an extension of the tunnel sidewalls, and they are further linked together by a bar 44 fitted The upstanding spigot formations 45 at their upper rear comers. The latter also provide a means of connection of the control cables 40, 40, which, as shown in FIG. 3, cross one over the other. These control cables 40, 40 lead forwardly through the hull structure 10 to a steering column assembly 48, mounted on a facia panel 49 at the front of the cockpit 17, by means of which the craft is steered.

in this embodiment, it will also be noted that the portion of the tunnel 12b immediately behind the bulkhead partition 14 which forms a front wall or stepped entrance to the main part of the tunnel housing the propeller 18 is vented towards the top by a pipe 50 which leads from the exhaust system of the engine power unit 16.

in operation, during the normal high speed operation under planing conditions for which the craft is designed, the hull will generally assume an attitude of about to the surface of the water so that the tunnel 12 also becomes inclined and the forward portion 12c is clear of the water and forms a front open ing into the main part of the tunnel. Air is therefore admitted, in advance of the propeller, at the front as well as from the exhaust vent 50. Although this admittance of air tends to reduce the normal suction effect produced by the craft in motion, the pressure under the hull generated by the motion of the craft is great enough to force water into the rear portion [2a of the tunnel to keep the propeller sufficiently immersed and it is found, somewhat surprisingly, that an effect of the admittance of air in advance of the propeller is to give a notable increase in performance. it is further believed that the abrupt step and change in depth provided by the partition wall 14 at the front end of the main part of the tunnel is advantageous and may contribute to the improved performance as well as providing a convenient mounting for the engine power unit.

At slow speeds and during acceleration, the greater angle of trim of the craft is sufficient to maintain the propeller end of the tunnel, 12a, filled with water.

Although the cross section shape of the tunnel and clearance of the propeller therein do not appear to be critical, the blade area of the propeller is important and must be within certain limits for a given size of craft. Also, the positioning of the propeller is important and in general, the distance of the propeller from the rear open end of the tunnel must be at least equal to its pitch. Also, if the propeller is too close to the forward end wall or bulkhead partition 14, efficiency will diminish.

One important advantage of the arrangement in accordance with the invention hereinbefore described is that the propeller need not protrude beneath the effective contour of the hull of the craft of which the tunnel is regarded as forming part, so that the craft can have a very shallow draught, and the shielding of the propeller removes the danger to swimmers and water-skiers and reduces the possibility of fouling due to foreign debris such as weed and rope which can easily be caught up by an exposed propeller. Also, the shielded propeller is safeguarded to some extent from direct damage if the craft is grounded or strikes debris, and it permits the craft to be handled more easily when out of the water. Thus, a small portable type of craft embodying a shielded propeller in accordance with this invention may, for example be more readily fitted to a car roof rack and can be transported more conveniently than similar craft with exposed propellers.

in the water, not only can a high speed performance be obtained, but good handling and maneuverability characteristics can be obtained in straight running and in sharp turns, and it is believed that the arrangement of the propulsion means described improves the stability and reduces tendencies for the craft to skid sideways on the surface of the water when planing and turning.

it may further be pointed out that the thrust line is maintained close to the horizontal, low down, and at approximately the same level as the line of resistance to the craft, thereby reducing couples which tend to exaggerate the planing angle of the craft. Also, a propeller of optimum dimensions and speed of rotation for maximum propulsion efficiency can readily be selected without producing many of the undesirable reactions obtained with conventional propeller arrangements.

Although the reasons for the improved overall propulsive efficiency are not fully understood, some improvement may perhaps be attributed to negligible intake losses compared, for example, with the scoop resistance losses on a water jet propulsion unit, and to a relatively small "wetted" area.

Also, as the appendage drag created by a conventional rudder or outboard engine can be eliminated by the twin rudder plate deflector arrangement described, which in effect forms an extension of the tunnel, this factor will further increase efficiency.

It will be appreciated that in a craft as herein described, the construction is basically simple and can be relatively cheap to produce, and furthermore the tunnel formation has a shape which tends to stiffen and strengthen the hull which is particularly advantageous when the latter is moulded integrally into a glass fiber reinforced plastics body structure.

it will, of course, also be understood that many other modifications or changes in constructional details may be made within the scope of the invention which is defined in the appended claims.

1. A power-driven high speed planing water craft having a hull, reentrant channel extending longitudinally which is open at the rear and which opens downwardly along the underside of the hull, a propeller disposed within a main tunnel section of said channel, a crosswall disposed forwardly which provides an abrupt step defining and at least partially closing the front end of said tunnel section, said crosswall constituting a bulkhead partition, an opening into said tunnel section adapted to admit gaseous medium therein above the water level and in advance of the propeller during planing operation of the craft, a cockpit compartment disposed forwardly of the bulkhead partition, an engine power unit located within said cockpit compartment, and drive transmission means which transmits drive from said engine power unit to the propeller.

2. A power-driven high speed water craft having a hull, a reentrant channel extending longitudinally which is open at the rear and which opens downwardly along the underside of the hull, a propeller disposed within a main tunnel section of said channel, a crosswall disposed forwardly which provides an abrupt step defining and at least partially closing the front end of said tunnel section, said crosswall constituting a bulkhead partition, and in advance of said erosswall, a shallow front tunnel portion which extends along the hull sufficiently for its front end to rise clear above the water when the craft is in an inclined position during planing operation, thereby to admit air under the hull and into said main tunnel section in advance of the propeller.

3. A power driven high speed planing water craft having a hull structure comprising a body shell, planing surfaces formed by the bottom of said body shell, a recess, reentrant with respect to the contour of the planing surfaces of said body shell, providing a channel disposed within the hull structure and extending forwardly from the stern, said channel being open at the rear adjacent the stern and downwards along the underside of the hull structure, a propeller operatively disposed within and towards the rear of said channel, a crosswall, disposed forwardly of the stern, which provides an abrupt step closing at least partially the front end of said channel, and an opening into said channel in advance of the propeller adapted to admit gaseous medium above the water level during planing operation of the craft.

4. A power-driven high speed planing water craft as defined in claim 3 wherein the channel rearwards of said crosswall comprises a main tunnel section and longitudinal side walls which define the sides of said tunnel section and flank the propeller, said propeller being housed within said tunnel section substantially completely above the level of the lowermost planing surfaces of the body shell which are effective during high speed planing operation.

5. A power driven high speed planing water craft as defined in claim 4 wherein the channel forwards of said crosswall comprises a shallow front tunnel section which has an open front end and which extends forwardly along the underside of the hull structure, within the contour of the body shell of said hull structure, sufficiently said open front end to rise clear above the water level when the draft is in an inclined position during planing operation, thereby to admit air under the hull structure and into said tunnel sections in advance of the propeller.

6. A power-driven high speed planing water craft as defined in claim 4 having a rudder system comprising a pair of angularly movable spaced-apart rudder plates secured to the hull structure, adjacent the stern, in contiguous relationship with the sidewalls of said main tunnel section thereby to provide an angularly variable rearwards extension of the latter, means linking together said rudder plates so that they remain parallel and move in unison, and control means for remotely adjusting the angular positioning of said rudder plates.

7. A power-driven high speed planing water craft as defined in claim 6 wherein the body shell of the hull structure, including said channel tunnel sections, is a molded lightweight unitary structure composed of glass fiber reinforced plastics material, and each of the rudder plates is composed of thermoplastics material and is adapted to flex, to provide the required angular movement, along a vertical hinge axis adjacent a leading edge portion which is secured to the respec tive sidewall of the main tunnel section in the hull structure.

8. A power-driven high speed planing water craft as defined in claim 4 wherein a vent opening into the main tunnel section is provided above the water line in the region adjacent said crosswall.

9. A powerdriven high speed planing water craft as defined in claim 4, wherein the crosswall at the front end of the main tunnel section constitutes a bulkhead partition, and said craft further comprises an inboard engine power unit mounted upon said bulkhead partition, drive transmission means including a propeller shaft which transmits drive from said engine power unit to the propeller, said propeller shaft being disposed wholly within the main tunnel section and within the contour of the planing surfaces of the hull body shell.

10. A power-driven high speed planing water craft as defined in claim 4 wherein a vent opening into the main tunnel section is provided by a shallow recess extending forwardly of said crosswall along a portion of the underside of the hull structure which rises clear above the water level when the craft is in an inclined position during planing operation, and wherein said hull structure has an uninterrupted surface extending continuously along each side of said main tunnel portion and along each side of said vent forwardly beyond the abrupt step leading into said main tunnel section.

11. In a power-driven high speed planing water craft, a hull structure, a tunnel portion of inverted U-shape reentrant within said hull structure and extending longitudinally from the stern, said tunnel portion being open rearwardly adjacent the stern and downwardly along the underside of the bottom of the hull structure, a crosswall closing at least partially the forward end of said tunnel portion and providing an abrupt step in the undersurface of said hull structure leading into said tunnel portion, a propeller housed within said tunnel portion towards the stern, planing surface portions, provided by the bottom of said hull structure, which are disposed laterally adjacent the downwardly presented open mouth of said tunnel portion and which extend below the level of said propeller, at opposite sides thereof, and inlet means adapted to introduce gaseous medium into said tunnel portion, in advance of the propeller, during planing operation of the craft.

12. A power-driven high speed planing water craft as defined in claim 11 wherein the bottom of the hull structure has an uninterrupted surface extending continuously along each side of said tunnel portion and forwardly beyond the abrupt step leading into said tunnel portion.

13. A power-driven high speed planing water craft as defined in claim 12 wherein the inlet means adapted to introduce gaseous medium into the said tunnel portion corn prises a shallow channel, forming a shallow front tunnel section, which is disposed forwardly of the abrupt step provided by said crosswall and which extends along the underside of the hull structure, within the contour of the body shell of said hull structure, sufficiently for said open front end to rise clear above the water level when the craft is in an inclined position during planing operation, thereby to admit air under the hull structure and into said tunnel sections in advance of the propeller. j

14. A power-driven high speed planing water craft as defined in claim 13 wherein the crosswall at the front end of the main tunnel section constitutes a bulkhead partition, and said craft further comprises an inboard engine power unit mounted upon said bulkhead partition, drive transmission means including a propeller shaft which transmits drive from said engine power unit to the propeller, said propeller shaft being disposed wholly within the main tunnel section and within the contour of the planing surface of the hull body shell.

15. A power-driven high speed planing water craft as defined in claim 14 having a cockpit compartment which is disposed forwardly of the bulkhead partition and which accommodates the engine power unit, flexible coupling means to connect said engine power unit to the forward end of the propeller shaft, and bearing means rotatably supporting the rear end of said propeller shaft, said bearing means and the propeller carried by the propeller shaft being housed in full shielded relationship completely within the tunnel portion within the contour of the bottom of the hull structure. 

1. A power-driven high speed planing water craft having a hull, reentrant channel extending longitudinally which is open at the rear and which opens downwardly along the underside of the hull, a propeller disposed within a main tunnel section of said channel, a crosswall disposed forwardly which provides an abrupt step defining and at least partially closing the front end of said tunnel section, said crosswall constituting a bulkhead partition, an opening into said tunnel section adapted to admit gaseous medium therein above the water level and in advance of the propeller during planing operation of the craft, a cockpit compartment disposed forwardly of the bulkhead partition, an engine power unit located within said cockpit compartment, and drive transmission means which transmits drive from said engine power unit to the propeller.
 2. A power-driven high speed water craft having a hull, a reentrant channel extending longitudinally which is open at the rear and which opens downwardly along the underside of the hull, a propeller diSposed within a main tunnel section of said channel, a crosswall disposed forwardly which provides an abrupt step defining and at least partially closing the front end of said tunnel section, said crosswall constituting a bulkhead partition, and in advance of said crosswall, a shallow front tunnel portion which extends along the hull sufficiently for its front end to rise clear above the water when the craft is in an inclined position during planing operation, thereby to admit air under the hull and into said main tunnel section in advance of the propeller.
 3. A power driven high speed planing water craft having a hull structure comprising a body shell, planing surfaces formed by the bottom of said body shell, a recess, reentrant with respect to the contour of the planing surfaces of said body shell, providing a channel disposed within the hull structure and extending forwardly from the stern, said channel being open at the rear adjacent the stern and downwards along the underside of the hull structure, a propeller operatively disposed within and towards the rear of said channel, a crosswall, disposed forwardly of the stern, which provides an abrupt step closing at least partially the front end of said channel, and an opening into said channel in advance of the propeller adapted to admit gaseous medium above the water level during planing operation of the craft.
 4. A power-driven high speed planing water craft as defined in claim 3 wherein the channel rearwards of said crosswall comprises a main tunnel section and longitudinal side walls which define the sides of said tunnel section and flank the propeller, said propeller being housed within said tunnel section substantially completely above the level of the lowermost planing surfaces of the body shell which are effective during high speed planing operation.
 5. A power driven high speed planing water craft as defined in claim 4 wherein the channel forwards of said crosswall comprises a shallow front tunnel section which has an open front end and which extends forwardly along the underside of the hull structure, within the contour of the body shell of said hull structure, sufficiently said open front end to rise clear above the water level when the draft is in an inclined position during planing operation, thereby to admit air under the hull structure and into said tunnel sections in advance of the propeller.
 6. A power-driven high speed planing water craft as defined in claim 4 having a rudder system comprising a pair of angularly movable spaced-apart rudder plates secured to the hull structure, adjacent the stern, in contiguous relationship with the sidewalls of said main tunnel section thereby to provide an angularly variable rearwards extension of the latter, means linking together said rudder plates so that they remain parallel and move in unison, and control means for remotely adjusting the angular positioning of said rudder plates.
 7. A power-driven high speed planing water craft as defined in claim 6 wherein the body shell of the hull structure, including said channel tunnel sections, is a molded lightweight unitary structure composed of glass fiber reinforced plastics material, and each of the rudder plates is composed of thermoplastics material and is adapted to flex, to provide the required angular movement, along a vertical hinge axis adjacent a leading edge portion which is secured to the respective sidewall of the main tunnel section in the hull structure.
 8. A power-driven high speed planing water craft as defined in claim 4 wherein a vent opening into the main tunnel section is provided above the water line in the region adjacent said crosswall.
 9. A power-driven high speed planing water craft as defined in claim 4, wherein the crosswall at the front end of the main tunnel section constitutes a bulkhead partition, and said craft further comprises an inboard engine power unit mounted upon said bulkhead partition, drive transmission means including a propeller shaft which transmits drive from said Engine power unit to the propeller, said propeller shaft being disposed wholly within the main tunnel section and within the contour of the planing surfaces of the hull body shell.
 10. A power-driven high speed planing water craft as defined in claim 4 wherein a vent opening into the main tunnel section is provided by a shallow recess extending forwardly of said crosswall along a portion of the underside of the hull structure which rises clear above the water level when the craft is in an inclined position during planing operation, and wherein said hull structure has an uninterrupted surface extending continuously along each side of said main tunnel portion and along each side of said vent forwardly beyond the abrupt step leading into said main tunnel section.
 11. In a power-driven high speed planing water craft, a hull structure, a tunnel portion of inverted U-shape reentrant within said hull structure and extending longitudinally from the stern, said tunnel portion being open rearwardly adjacent the stern and downwardly along the underside of the bottom of the hull structure, a crosswall closing at least partially the forward end of said tunnel portion and providing an abrupt step in the undersurface of said hull structure leading into said tunnel portion, a propeller housed within said tunnel portion towards the stern, planing surface portions, provided by the bottom of said hull structure, which are disposed laterally adjacent the downwardly presented open mouth of said tunnel portion and which extend below the level of said propeller, at opposite sides thereof, and inlet means adapted to introduce gaseous medium into said tunnel portion, in advance of the propeller, during planing operation of the craft.
 12. A power-driven high speed planing water craft as defined in claim 11 wherein the bottom of the hull structure has an uninterrupted surface extending continuously along each side of said tunnel portion and forwardly beyond the abrupt step leading into said tunnel portion.
 13. A power-driven high speed planing water craft as defined in claim 12 wherein the inlet means adapted to introduce gaseous medium into the said tunnel portion comprises a shallow channel, forming a shallow front tunnel section, which is disposed forwardly of the abrupt step provided by said crosswall and which extends along the underside of the hull structure, within the contour of the body shell of said hull structure, sufficiently for said open front end to rise clear above the water level when the craft is in an inclined position during planing operation, thereby to admit air under the hull structure and into said tunnel sections in advance of the propeller.
 14. A power-driven high speed planing water craft as defined in claim 13 wherein the crosswall at the front end of the main tunnel section constitutes a bulkhead partition, and said craft further comprises an inboard engine power unit mounted upon said bulkhead partition, drive transmission means including a propeller shaft which transmits drive from said engine power unit to the propeller, said propeller shaft being disposed wholly within the main tunnel section and within the contour of the planing surface of the hull body shell.
 15. A power-driven high speed planing water craft as defined in claim 14 having a cockpit compartment which is disposed forwardly of the bulkhead partition and which accommodates the engine power unit, flexible coupling means to connect said engine power unit to the forward end of the propeller shaft, and bearing means rotatably supporting the rear end of said propeller shaft, said bearing means and the propeller carried by the propeller shaft being housed in full shielded relationship completely within the tunnel portion within the contour of the bottom of the hull structure. 